From b6c2bfea096ba22583f1071c10ce0745804b9b95 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Tue, 9 Feb 2021 10:32:20 -0500 Subject: svcrdma: Relieve contention on sc_send_lock. /proc/lock_stat indicates the the sc_send_lock is heavily contended when the server is under load from a single client. To address this, convert the send_ctxt free list to an llist. Returning an item to the send_ctxt cache is now waitless, which reduces the instruction path length in the single-threaded Send handler (svc_rdma_wc_send). The goal is to enable the ib_comp_wq worker to handle a higher RPC/RDMA Send completion rate given the same CPU resources. This change reduces CPU utilization of Send completion by 2-3% on my server. Signed-off-by: Chuck Lever Reviewed-By: Tom Talpey --- include/linux/sunrpc/svc_rdma.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h index 57c60ffe76dd..5f8d5af6556c 100644 --- a/include/linux/sunrpc/svc_rdma.h +++ b/include/linux/sunrpc/svc_rdma.h @@ -90,7 +90,7 @@ struct svcxprt_rdma { struct ib_pd *sc_pd; spinlock_t sc_send_lock; - struct list_head sc_send_ctxts; + struct llist_head sc_send_ctxts; spinlock_t sc_rw_ctxt_lock; struct list_head sc_rw_ctxts; @@ -150,7 +150,7 @@ struct svc_rdma_recv_ctxt { }; struct svc_rdma_send_ctxt { - struct list_head sc_list; + struct llist_node sc_node; struct rpc_rdma_cid sc_cid; struct ib_send_wr sc_send_wr; -- cgit v1.2.3-71-gd317